Photographic copying apparatus stripping mechanism



Jan. 10, 1967 E. F. sTlEvENART 3,297,317

PHOTOGRAPHIC COPYING APPARATUS STRIPPING MECHANISM Filed June 30, 1964 3 Sheets-Sheet l l 0+ i l 4f A M gm l Z6 57 #Q INVENTOR zz'le Ziff/emr@ BY/W Y %d ATToRNEx/,s

Jan. l0, 1967 E, F. sTlEvENART 3,297,317

PHOTOGRAPHIC COPYING APPARATUS STRIPPING MECHANISM Filed June 30, 1964 3 Sheets-Sheet 2 INVENTOR ATTORNEY Jan. 10, 1967 E. F. sTlEvENART 3,297,317

PHOTOGRAPHIC COPYING APPARATUS STRIPPING MECHANISM Filed June 30, 1964 3 Sheets-Sheet, 5

INVENTOR BYZMM My waan ATTORNEYS United States Patent C M 3,297,317 PHOTOGRAPHIC COPYING APPARATUS STRIPPING MECHANISM Emile Frans Stievenart, Kiel-Antwerpen, Belgium, assignor to Gavaert-Agfa N.V., Mortsel, Belgium, a Belgian company Filed July 30, 1964, Ser. No. 386,189 13 Claims. (Cl. 271-64) This invention relates generally to document copying devices and more specifically to an improved copy sheet stripping mechanism for a photographic copying device of the image-transfer type.

Photographic copying devices in which an exposed light-sensitive sheet is urged in the presence of suitable processing liquid into intimate contact with an imagereceiving sheet are well known in the art. Little attention, however, has been paid to the problem of separating by means of mechanical instrumentalities the damp, tightly adhering sheets from each other.

One device adapted for the separation of such sheets is disclosed in pending United States application Serial No. 310,826 commonly assigned with this application. The essential feature of this device is a separating knife which is urged between the sheets, after they have been completely pressed onto each other. While the results obtained with this device were considerably better than those hitherto known in the art, the accurate mounting of the knife and of the means for introducing it between the sheets needed for minimizing the risk of damaging the sheets did give rise to some mechanical problems.

Another approach to the problem described above, that is less subject to rigid design specifications is disclosed in copending United States application Serial No. 361,728, also commonly assigned with this application. This approach contemplated the provision of sheet material advancing means for positively gripping the leading margin of one material at a fixed locus on the path of movement of the adhering .sheets and means operable to exert a rubbing action generally uniformly across the exposed face of the other material just in advance of said fixed locus and prior to any engagement of said other material by said advancing means, whereby a tendency to curl and to separate from the first material is imparted to the other material.

Although the risk of sheet damage is reduced with the latter device, it is subject to an inconvenience, inherent also in the first device, viz. the front edge of one definite sheet has to lead that of the other by a definite distance. This means that the two sheets have to be assembled in rather precise fashion prior to feeding the assembly to the separating mechanism. Although controlled assemblage may be considerably facilitated by appropriate design yof the paths followed by the sheets in the apparatus before arrival at the point of merger to prolong one path relative to the other, s that the operator has only to bring the leading margins of the two sheets into registration prior to their introduction in the device, experience has shown that even this simple step of registering the sheet edges is not always properly performed if the device is handled by an unskilled or absent-minded operator,

It is an object of the present invention to provide a copying apparatus for separating a light-sensitive sheet from an intimately-adhering, image-receiving sheet which affords greater flexibility in the relationship of the leading edges of the sheets than has heretofore been possible inthe art.

The above statement should not be read as suggesting that the sheets to be separated can take any possible relative position, but rather that within reasonable limits, say 1/2 inch in either forward or backward direction,

3,297,317 Patented Jan. 10, 1967 the relationship of the sheet leading edges as well as the correlation of the top or bottom sheet with the leading or trailing position is not critical to the successful operation of the system.

Another object of the present invention is to provide a stripping mechanism which is not dependent upon precise orientation `of its moving parts and is, therefore, reliable in operation and needs little, if any adjustment.

Still another object of the invention is to provide a stripping mechanism that isV of compactdesign and, thus, especially well adapted for operative association with commercially available copying apparatus by the manufacturers of such apparatus, without considerable changes in the construction and design of the apparatus. 'l

In broad perspective, the present invention accomplishes the separation of an image-receiving sheet from a light-sensitive `sheet intimately adhering thereto by an arrangement, comprising'means for frictionally engaging one of said sheets of said sandwich adjacent the leading margins thereof to temporarily immobilize said sheet against movement, and means for applying a dynamic frictional force to the exposed face of said other sheet along a limited longitudinal locus adjacent its leading margins, said force being directed generally away from said margins and of sufficient magnitude to overcome the coeicient of Yfriction between the contacting faces of said sheets and buckle said vother sheet away from said first sheet, and means for supporting said sandwich against said force at least in the areas of its application. The mentioned friction applying means may be and preferably are rotatable friction rollers, but it is Vclear that other forms of friction means such as rotating rubber fingers, resilient disks which are axially spaced on a rotating shaft, etc., may find application for this purpose. One noteworthy advantagey of a stripping mechanism according to the present invention is its suitability for the separation of the adhering materials not only when both are wetted by the processing liquid necessary t-o the diffusion transfer prior to being pressed into contact, but when just one of the materials is wetted by the processing liquid, and even when only enough of the liquid as to spread over the interface of the materials is present. In the latter two methods the minimum quantity of liquid used results in strong adherence of the sheets with the important incidental advantage that the sheets forming the ultimate copies -are dry or almost so after separation. v The device according to the present invention is particularly suited for producing copies according tothe now well-known silver halide ldiffusion transfer process. In this process, as those skilled in the art are aware, a light-sensitive material including a silver halide emulsion layer is image-wise exposed to an original and pressed against an image-receiving material in the presence of a processing liquid, which contains, among other constituents, a developing agent and a silver halide complexing agent, whereby the unexposed and undeveloped parts of the silver halide are complexed and diffuserto the image-receiving material, where they are converted into a silver image by the action of developing nuclei. The basic disclosure of the diffusion transfer process appears in United States Patent 2,352,014 to Rott and numerous improvements have now appeared in the patented art, to which reference may be had if desired for the details involved in the practice of this process. While certain particular materials have been found especially well adapted for use in the apparatus of this invention, as will be hereinafter explained, it has general application in the field of diffusion transfer and is not limited to these or any other specific materials.

The invention will be further explained by the following examples and illustrated by the accompanying drawings, in which:

FIGS. la-ld are diagrammatic views illustrating the step-by-step operation of the present concept, with the following stages being depicted:

FIG. la shows the arrival of the sheets at a pair of cooperating friction rollers rotating in the indicated direction to initially advance the sheet,

FIG. 1b shows the actuation by the advancing sheets of a sensing device behind the nip of the separating rollers,

FIG. lc shows the reverse rotation of one of the rollers while the other is momentarily stilled to bring about the separation of the leading portions of the sheets, and

FIG. ld shows the completion of the separation;

FIG. 2 is a side view partially in section of a simplitied copying apparatus embodying the principles of this invention;

FIG. 3 is a detail view of the mechanism controlling the displaceable means for guiding the two sheets, with certain parts shown in dotted lines for clearer understanding;

FIG. 4 is a top view of the driving system for the various rollers in the embodiment of FIG. 2; and

FIG. 5 is the electrical circuit of the apparatus of FIG. 2.

For sake of clarity, in FIGS. la-ld, both the sheets and the friction rollers have been shown in slightly spacedapart relationship, although contact therebetween would naturally be present in practice. As can be seen in these figures, a first sheet and a second sheet 11, adhering together because of the presence of moisture or other liquid between their contacting surfaces, are advanced in the direction of the arrow at the left of FIG. la towards the nip of rollers 12 and 13 Which resiliently press onto each other. Both rollers are rotating in the directions indicated by the respective arrows and assume control over the advance of the sandwich of the sheets upon its entry between the rollers (FIG. 1b), forwarding the sandwich until its leading edge actuates a sens ing device 14, controlling the mechanism (not shown in FIGS. la-ld) for driving the rollers. This mechanism is so designed as to reverse the direction of rotation of the roller 12 and to arrest the roller 13 in response to the actuation of the sensing device 14. The advance of the sheet 11, nearest roller 13, is temporarily halted, whereas the leading portion of the sheet 10, adjacent roller 12, is rubbed backwardly, causing the sheet to curve and form a loop 15 (FIG. 1c) until the leading edge of the sheet passes around and finally above roller 12. After a given period of reverse rotation, which period is at least long enough to permit the leading edge of sheet 10 to pass over the roller 12 as just described, the direction of rotation of said roller is reversed again (FIG. ld) so as to renew the advance of the sheet 11 and, as a consequence of the adhering relationship, that of the now-freed leading edge of the sheet 10 also. As the looped portion of the sheet 10 clears the periphery 0f roller 12 and straightens ou-t above the roller, its leading edge is engaged by a pair of continuously turning small rollers 16 arranged at the proper location for this purpose. In this way, the possibility of the sheet 10 being rubbed backwardly and folded upon itself when the rollers are again rotated in their loriginal direction to continue the advance of the sheet 11 is avoided.

For the operation of the device it is essential that the degree of adherence of the two sheets to each other, i.e. their mutual attraction, is less than the coeicient of friction between each of the sheets and its corresponding roller. Suicient friction between the rollers and the sheets can be obtained by roughening the surface of the rollers, or by providing them with a layer of a resilient material such as natural rubber or foam rubber, or their synthetic equivalents.

It will be apparent from the figures under discussion 'that exact positioning of the sheets relative to one another is not necessary. The sheet 10 could, for example, as well be in registration with, or behind, as to lead sheet 11. Care shall be taken, however, that the distance between the leading edges of the sheets does not exceed the distance between the nip of the rollers 12, 13 and the sensing device controlling the rotation of the one roller, since the second sheet must obviously be within the nip of the rollers when the reversal takes place.

An embodiment of a separating mechanism according to the invention, is shown in FIG. 2 in operating association with a copying apparatus of the diffusion transfer type. This copying apparatus, which is typical of the construction of a number of commercially available models, comprises a housing 20 for holding the processing liquid 21, an array of guide plates 22, and a pair of pressure rollers 23-24 adjacent the outlet of the housing.

The mechanism for separating Ithe sandwich of both sheets comprises the rollers 25, 26, 27 as well as the roller pair 1S, 28 for conveying the separated imagereceiving sheet 10 and the roller 29 with the roll 30 for receiving the separated light-sensitive sheet 11.

The roller 27 is driven by means of electric motor 31 through the intermediary of a reversing gear 32 (FIG. 4), capable of driving the roller 27 either in the forward direction so as to continue the advance of the sheets as they arrive from the copying apparatus (counterclockwise rotation of roller 27 in FIG. 2), or in the reverse direction (clockwise rotation of roller 27 in FIG. 2).

The roller 27 has, for example, a diameter of l0 mm. is made of stainless steel and may and preferably does have a roughened surface, e.g. applied by milling.

The roller 26 has a diameter of 35 mm. and consists of a hollow plastic cylinder which is covered With a resilient layer 33 of rubber or the like. It is mounted for free rotation on a stationary shaft 34, being driven by frictional contact with the periphery of the roller 27. The execution of Ithe differential frictional effect upon the two adhering sheets requires that roller 26 be restrained against rotation except in the direction of the advance of the sheets (clockwise in FIG. 2). To this end, roller 26 is provided with a pawl 35, rotating bodily therewith, which under the influence of spring means (not shown) engages a ratchet wheel 35 which is rigidly locked to the stationary shaft 34. As it clearly appears from the drawing, the pawl 35 can only rotate in the clockwise direction around the ratchet wheel 36.

Beneath roller 26 is a pressure roller 25 also preferably made of stainless steel, Iand mounted for free rotation around its shaft. The drive of said roller is derived by frictional contact with the roller 26. Roller 25 is needed mainly by reason of the sinuous configuration of the particular path of the sheets in the illustrated embodiment and with other paths it could be dispensed with.

The pressure between the rollers 26 and 27 which is required for the proper `operation of the apparatus and which depends for the greater part on the nature of the roller surface and for a minor part on the kind of sheet materials which are used in the apparatus since they are less subject to important differences, is adjustable by means of the screws 74, 75 which press on the slidably kmounted bearings 72, 73 of the roller 27. Besides the adjustment of the proper pressurebetween both rollers, the screws 74, 75 permit also the uniform distribution of the pressure over the roller length. The displacement of the shaft of the roller 27 for different adjustments of -the roller pressure was so small in the present apparatus, that no flexible coupling between the shaft of the reverse gear 32 and the roller shaft was required.

Extending generally tangentially of the nip of rollers 26, 27 on the downstream side thereof is a feed plate 37 of metal, plastic or the like for receiving the light-sensitive sheet 11 after separation has -been effected. Preferably, the mechanism includes means for collecting the discarded sheets 11, one inexpensive arrangement for this purpose being shown in FIG. 2. Thus, a roller 29 is disposed at the remote end of plate 37 with its periphery projecting just above the plane of plate 37. Resting on roller 29 is a freely rot-atable roll 30 having each of its ends journaled in an elongated vertical slot 39 in a supporting bracket 40 Ito permit roll 30 a substantial extent of vertical movement away from roller 29. Roll 30 is preferably of disposable construction, being formed, for instance, as a hollow core of cardboard or the like. Roller 29 is continuously driven in 4a clockwise direction while roll '30 turns at the same peripheral speed under its own weight on roller 29.

Near the end of plate 37 adjacent the rollers 26, 27 is a sensing device, in ythe present case a microswitch 60 having a contact finger projecting into the path of the sheets emerging from between rollers 26, 27. It is clear that other means responsive to the arrival of the sandwich such -as photoelectric cells or photoresis-tors may likewise Vbe used at this stage.

Upon the arrival of a used light-sensitive sheet between the nip of the roller 29 and the roll 30, the upwardly facing damp emulsion layer instantly adheres to roll 30 so that the sheet :becomes entirely wrapped around the roll 30 as roller 29 rotates. As the number of sheets wrapped around the said roll increases, its diameter increases accordingly. When a given maximum permissible diameter has been reached, accompanied, if desired, by a warning signal emanating from a suitable mechanical or electrical detecting means, the roll is lifted out of the slots 39, discarded, and replaced with a new core 3S. The distance between the nips of rollers 26, 27 and roller-core 29, 38 should be less than the length of the sheets being processed if the collection is to occur automatically.

The drive mechanism for the respective rollers of the apparatus is shown in FIG. 4, and comprises an electric motor 31 with -associated reduction gear, driving directly the outlet roller pair 23, 24 and the reversing gear 32. The roller 29 and the roller pair 18, 28 are driven by rneans of a belt take-off from the shaft of roller 23. The peripheral speed of the roller 29 is selected to be equal to or slightly higher than that of the roller 27.

The gear-ratio of the reversing gear 32 is such that in the forward direction the peripheral speed of the roller 27 is equal to that of the roller pair 23, 24, and in the reverse direction is equal to or higher than that of such pair. The reversing gear normally turns in a forward direction, whereas for the reverse direction a control lever 44- is shifted by means of a solenoid 45 (FIG. 5) to which it is hingedly connected by means of a rod 46, to the position as shown in dot-dash lines.

A further adjunct used by reason of the particular design of FIG. 2 is a number of arcuate guide lingers 47 arranged at spaced intervals over the length of the roller 26 and supported by a pivotable shaft 48. This shaft is provided -on one extremity with the lever 49 which can take two extreme positions, as shown in solid lines and in dot-dash lines, respectively, in FIG. 3. The movement of lever 49 between these positions is controlled as follows:

A disk-shaped member 50 is coaxially mounted at one extremity of the shaft 51 which carries roll-er 27 and in frictional engagement with the shaft surface. Upon rotation of the shaft 51 in either direction, the disk 50 rotates together with the shaft until a lug 52 provided for this purpose at a point of the periphery of disk 50 abuts against one of the fixed abutments 53, 54. Continued rotation of shaft 51 results in disk 50 slipping on the shaft to one of its limiting positions determined by the location -of the abutments 53, 54.

So long as shaft 51 rotates in a counterclockwise direction, a tension spring 55 acts upon .lever 49 to keep fingers 47 in a position generally concentric to but slightly spaced from the periphery of lroller 26. When in this position, fingers 47 stretch approximately the full distance between the rollers 23 and 27 and serve to positively guide the sheet s-andwich upon delivery from the nip of roller 25 and roller 26 to the nip of roller 27 with roller 26.

When the shaft 51 rst starts to rotate in a clockwise direction, however, the disk 50 pushes through the lug 52 against the lever 49, pivoting the latter against the force of tension spring 55 to the left in FIG. 3. By this movement, shaft 48 is pivoted in a counterclockwise direction so that the free ends of tingers 47 swing away from the periphery of the roller 26. The new position of the fingers 47 and of the lever 49 is shown in dot-dash lines in FIG. 3. In this gure, the periphery of the rollers 27 and 26 has been indicated in broken lines to avoid confusion.

In the event the conventional copying apparatus does not already include an outlet guide channel adapted to delivery of the sandwich to the separating mechanism at `the desired point and inthe proper direction, such a channel can be advantageously provided, as shown at `61, 62. Should the length of channel 61, 62 exceed that of the sheets being processed, supplementary feed rollers at an appropriate `point along the channel will be needed.

The operation of the entire apparatus of FIG. 2 is as follows:

An image-receiving sheet 10 is introduced, its imagereceiving face directed downwardly, together with an already image wise exposed light-sensitivel sheet 11 having emulsion face directed upwardly, into the respective channels dened by the guide plates 22 in housing 20.

The image-receiving sheet 10 follows the path numbered 57 and the light-sensitive sheet 11 follows the path numbered 58. After passing through the processing liquid 21, both sheets are squeezed between the pressure roller pair 23, 24 and leave housing 20 adhering to each other. The diffusion transfer starts when the sheets come in contact.

In introducing the sheets to housing 20, care must be taken to insure that -one sheet does not lead the other on emergence from the pressure rollers 23, 24 a distance which exceeds the spacing between the nip of the rollers 26, 27 and the contact finger of the microswitch 60.

The rollers 23, 24 feed the sheets upwardly between the guide channel 61, 62 until the leading edge of the sandwich of both sheets enters the nip between the rollers 25, 26. These rollers are continuously rotating under the influence of the roller 27 rotating in anti-clockwise direction by the forward position of the reverse gear, and continiue the advance of the sheets also after the trailing edge of the sandwich has left the rollers 23, 24.

The fingers 47, which are at this point in the position as shown in solid lines, guide the sandwich around the roller 26 during its further rotation and direct its leading edge into the nip of the rollers 26, 27. As that edge emerges from the nip, it actuates the contact finger of the microswitch 60 which normally is biased by spring means (not shown) so as to obstruct the path indicated at 63 of the sandwich over t-he support plate 37, the electrical contact of the microswitch switching over from the position as indicated in solid lines in FIG. 5 to the position as indicated in broken lines. Thereby, a capacitor 64 which has been previously charged to the D.C. potential of supply lines 65, is connected to the relay 67, and starts to discharge through the parallel connection of the variable resistor `66 and the resistance of the coil of relay 67. The relay 67 which is excited by the potential of the capacitor 64 closes the electric circuit of the solenoid 45 by means of its closed contacts 70, and through the intermediary of the connecting rod 46 the reversing gear 32 is changed over.

Consequently, the roller 27 starts rotating in reverse direction, and incidentally thereto the ngers 47 are removed from the roller 26, until the capacitor 64 has discharged so far that its potential is no longer capable of further exciting the relay 67.

During reverse rotation of roller 27, the sheet 10 is rubbed backwardly and its leading portion bulges or loops as can be seen in FIG. lc, which bulging movement is permitted by the remote position of fingers 47. When the leading portion of sheet 10 rides free -of the engagement of the rollers 26, 27, it tends to straighten and extend tangentially to the roller 26 at a point 66 spaced backwardly from roller 27. During the reverse rotation of the roller 27, roller 26 is held xed on its shaft 34 by means of the ratchet mechanism 35, 36 so that the sheet 11 which rests lon its periphery does not change position, thereby continuing to actuate with its leading edge the microswitch 60.

When the relay 67 is deenergized, the solenoid 45 is released and, consequently, the reversing gear 41 will rotate again in the forward direction. The light-sensitive sheet 11 continues along path 63 over the support plate 37 until it becomes wrapped onto the roll 30, whereasthe image-receiving sheet 10 is directed between the continuously turning roller pair 18, 28 which forces the sheet upwardly over the support plate 41 along the path indicated at 42. These rollers occasionally may squeeze olf any remaining processing liquid adhering to the sheet. The said rollers may also be heated so as to accelerate the drying of the image-receiving sheet whereby it may be possible to produce copies which are almost dry upon leaving the apparatus. Occasionally, the acceleration of the drying of the image-receiving sheet may also be performed with the aid of other means, e.g. by a hot air blast, by completely or partially heating the support plate 41, etc.

When the trailing edge of the sheet 11 has passed the Contact nger of the microswitch 60, the latter is urged by spring means back to its position obstructing the path 63 (FIG. 2) and as electrically shown by the solid line in the electrical circuit (FIG. 5), so that the capacitor 66 Will be charged again to the potential of line 65. The time required for recharging capacitor 66 is suiciently short as to have the capacitor fully charged when the next sandwich, even when closely following the preceding one, reaches the microswitch.

Obviously, successive sandwiches should be maintained spaced apart a distance at least equal to the distance of transport corresponding to the, period of arrest of the roller 26, i.e. the period of the reverse rotation of the roller 27, to avoid overlapping of the sandwiches and unsatisfactory operation.

The time constant of the parallel RC circuit comprising the capacitor 64, the resistor 66 and the relay 67 should be great enough to permit reverse rotation of the roller 27 for a period long enough to insure that the leading margin of sheet 11 is entirely disengaged from beneath roller 27.

When the roller 27 starts to rotate again in the forward direction after its rotation in the reverse direction and the projection 52 of the disk 50 returns to the position as shown in solid lines in FIG. 3, the fingers 47 will not immediately resume their initial position towards the periphery of roller 26, but will be held somewhat removed therefrom by the continued presence of the sheet as the same is tangentially withdrawn from the roller 26 by the -roller pair 18, 28. When the sheet 10 has left the roller 26, the ngers are then free to pivot under the action of the tension spring 55 the remaining way to their solid line position.

In one satisfactory model of an apparatus constructed as in FIG. 2-5, the peripheral speed of the rollers was established at 4 cm./s., the time constant of the RC circuit was set by means of the variable resistor 66 to 4 seconds, the distance between the nip of rollers 26, 27 and the lever of the microswitch 60 amounted to 1.5 cm. The capacity of roll 30 was found to be 100 standard sheets of 21.5 x 27.5 cm. The time for producing a copy, re-

o ginning with the introduction of the sheets between the guides 22 amounted to 22 seconds. During the transfer process, the sheets remained in Working contact with each other for 8 seconds. After the separated imagereceiving sheet has completely dried, it was found that the deformation of its leading margin caused by the bulging during the reversed rotation of the roller 27 had virtually completely disappeared. A

Practical experience proved that excellent results can be obtained with the above-described apparatus when a light-sensitive sheet and an image-receiving sheet are used, provided that the tendency of the sheets to adhere to each other is not too strong. This tendency can be readily controlled by those skilled in the art by the selection of the compositions of the contacting layers thereof.

In the latter respect, sheets utilizing as the binding agents of the top layer of the light-sensitive sheet materials essentially different from those used as the binding agents of the top layer of the receiving sheet are particularly advantageous.

Materials which are especially suited for use in apparatus according -to the present invention are disclosed in the U.S. patent `application Serial No. 187,437, now abandoned describing a process for the production of images according to the silver complex diffusion transfer process, wherein the light-sensitive sheet, consisting of the usual support carrying a silver halide emulsion layer, is given an after-layer of a gelatin-free water-permeable colloid, and the receiving sheet is selected from the group consisting of paper, plastic iilm and textile materials; and in the U.S. patent application Serial No. 300,099 describing a similar process wherein the light-sensitive sheet bearing a silver halide emulsion layer and a water-permeable externa] layer, and an image-receiving sheet comprises a support and an uppermost layer containing a binding agent and a filler.

Separation of the sheets as described herein can also be facilitated by orienting the sandwich along a curved path at least just preceding the nip of the reversible roller. Such an orientation, as illustrated in FIG. 2, for example, capitalizes upon the inherently greater tendency of curved sheets to separate.

It is possible to further reduce the time required for producing a copy with the present apparatus by raising the temperature of the processing liquid, as for example, by providing an electrical heating element under the container of processing liquid 21 with a suitable thermostatic control, or by heating the sheets pressed against each other by means of heated rollers or a hot air blast.

The application of the processing liquid to the sheets may be done in Ways different from the one contemplated in the foregoing example. Itis thus possible to use a copying apparatus having a lick-roller applicator system for applying the processing liquid to the emulsion side of the light-sensitive material, a squeegee station for removing the excessive processing liquid from the lightsensitive material, and a pressing station for pressing the moistened light-sensitive sheet against the dry image-receiving sheet. A said apparatus is particularly interesting in case dry or virtually dry copies have to be produced without resorting to the use of heating means for accelerating the drying. The extremely small amount of liquid which is transferred during the process, makes that the image-receiving sheet, after its pathing through the pressure rollers 18, 28, is almost dry.

Alternatively, one can supply each time a measured quantity of fresh processing liquid for each copy to be produced. In that case, the opportunity for deterioration or oxidation of the processing liquid by air is eliminated.

Finally, the supply of processing liquid 21 can be omitted entirely where the image-receiving sheet and/or the light-sensitive sheet includes a rupturable capsule filled with processing liquid which is spread over the contacting surfaces when pressing the light-sensitive sheet against the image-receiving sheet.

The processing liquid 21 may also be omitted when the formation of the image in the image-receiving sheet is produced by heating specially-prepared sheets While pressed together, the sheets containing, besides the substances required for the formation of the image, compounds which, upon heating, release free water or hydrolyze and release an alkaline substance, together with hydrophilic softening agents.

I claim:

1. In a copying apparatus wherein light-sensitive sheet material is intimately brought by sheet-pressing means into sandwich relationship with an image-receiving sheet material and subsequently separated therefrom, the improvement of a mechanism for separating sheets delivered thereto, comprising means for frictionally engaging Yone of said sheets of said sandwich adjacent the leading edge thereof to temporarily immobilize said sheet against movement, and means for applying a dynamic frictional force to the exposed face of said other sheet along a limited longitudinal locus adjacent its leading edge, said force being directed generally away from said edge and of sufficient magnitude to overcome the coefficient of friction between the contacting faces of said sheet and buckle said other sheet away from said iirst sheet, means for supporting said sandwich against said force at least in the areas of its application, means for removing said first sheet from between said frictional force-applying means and said supporting means after said other sheet has buckled, and means for guiding the other sheet away from said first sheet as the same is removed.

2. The copying apparatus as in claim 1 wherein the first sheet is removed by reversing the frictional force applying means to advance the sheet.

3. A device as in claim 2, wherein the reverse speed of .the reversible roller is substantially greater than its forward speed.

4. The copying apparatus as in claim 1 wherein said guiding means including means for positively withdrawing said other sheet.

5. A mechanism for separating an image-receiving sheet from a light-sensitive sheet to which it is in intimately adhering, sandwich relationship comprising a rst roller and a second roller having their peripheries in resilient contact in the absence of sheets therebetween, means for guiding the sandwich of both sheets to the nip of both rollers, means for driving both rollers to initially advance the sandwich in its direction of travel, sensing means behind the nip of said rollers to detect the presence of the leading edge of the sandwich for passage thereof through the nip of the rollers, means responsive to said sensing means to control said driving means to temporarily arrest the rotationof one roller and reverse the rotation of the other roller whereby -tthe advance of one sheet is arrested and the leading portion of the other sheet is rubbed backwardly thereby buckling and separating from the said one sheet and assuming a position on the other side of said reverse-rotating roller, said responsive means thereafter restoring said other roller to the original direction of rotation to continue the advance of the arrested sheet while said other sheet passes on the other side of said other roller.

6. A mechanism as in claim 5, wherein the driving means for said rollers includes an electric motor coupled to said reversible roller through a reversing gear, the momentum for .the other roller inthe direction of the advance of the sheets being derived by frictional contact With the reversible roller, and the arrest thereof against the opposite direction being performed by means of a cooperating ratchet and pawl.

7. A mechanism as in claim 5 wherein the diameter of said reversible roller is substantially smaller than that of the other rollers.

8. A mechanism as in claim 7, wherein means are provided for guiding the sandwich around at least a portion of the periphery of the roller with the greater diameter so as to orient the same along a curved path before its entry into the nip of the rollers.

9. A device as in claim 8 wherein said guiding means is displaceable adjacent the nip of said roller to permit the buckling and ultimate separation of the leading portion of the sheet lying remote of .the periphery of the roller with the greater diameter.

10. A device as in claim 8, wherein the displacement of the guiding means occurs in response to the reversal of the reversible roller.

11. A mechanism as in claim S, wherein the means responsive to the sensing means includes a timing means effective to reverse the direction of rotation of said reversible roller during a predetermined period, after detection by said sensing means of the leading edge of said sandwich.

12. A mechanism as in claim 5 including means for engaging the separated leading portion of said other sheet and for withdrawing the same in synchronism to said first sheet.

13. In a copying apparatus wherein light-sensitive sheet material is intimately contacted by sheet-pressing means into sandwich relationship with an image-receiving sheet material and subsequently separated therefrom, a mechanism for separating sheets delivered thereto, comprising support means adapted for frictional contact with one exposed face of said sandwich, said means being movable in one direction to advance the sandwich longitudinally in a given direction and restrained against movement in the other direction, a friction member in opposed contacting relation to said support means at a fixed locus on the path thereof, said friction member being adapted for limited longitudinal engagement with the other eX- posed face of said sandwich while supported by said support means, and being cyclically movable about said locus, means for positively driving at least one of said support means and said frictional member to advance a sandwich delivered thereto in said one direction, sheet material detecting means arranged to sense the engagement of said sandwich between said member and said support, and means actuated in response tQ said detecting means for positively driving said friction member in a direction opposite to said given direction while said support means is constrained against like movement.

References Cited by the Examiner UNITED STATES PATENTS 2,042,734 6/ 1936 Roy 271-21 2,766,044 10/ 1956 Schulze 271-64 X 2,813,717 11/1957 Mentzer.

2,860,875 11/1958 Staeger 271-21 M. HENSON WOOD, IR., Primary Examiner.

R. A. SCHACHER, Assistant Examiner, 

1. IN A COPYING APPARATUS WHEREIN LIGHT-SENSITIVE SHEET MATERIAL IS INTIMATELY BROUGHT BY SHEET-PRESSING MEANS INTO SANDWICH RELATIONSHIP WITH AN IMAGE-RECEIVING SHEET MATERIAL AND SUBSEQUENTLY SEPARATED THEREFROM, THE IMPROVEMENT OF A MECHANISM FOR SEPARATING SHEETS DELIVERED THERETO, COMPRISING MEANS FOR FRICTIONALLY ENGAGING ONE OF SAID SHEETS OF SAID SANDWICH ADJACENT THE LEADING EDGE THEREOF TO TEMPORARILY IMMOBILIZE SAID SHEET AGAINST MOVEMENT, AND MEANS FOR APPLYING A DYNAMIC FRICTIONAL FORCE TO THE EXPOSED FACE OF SAID OTHER SHEET ALONG A LIMITED LONGITUDINAL LOCUS ADJACENT ITS LEADING EDGE, SAID FORCE BEING DIRECTED GENERALLY AWAY FROM SAID EDGE AND OF SUFFICIENT MAGNITUDE TO OVERCOME THE COEFFICIENT OF FRICTION BETWEEN THE CONTACTING FACES OF SAID SHEET AND BUCKLE SAID OTHER SHEET AWAY FROM SAID FIRST SHEET, MEANS FOR SUPPORTING SAID SANDWICH AGAINST SAID FORCE AT LEAST IN THE AREAS OF ITS APPLICATION, MEANS FOR REMOVING SAID FIRST SHEET FROM BETWEEN SAID FRICTIONAL FORCE-APPLYING MEANS AND SAID SUPPORTING MEANS AFTER SAID OTHER SHEET HAS BUCKLED, AND MEANS FOR GUIDING THE OTHER SHEET AWAY FROM SAID FIRST SHEET AS THE SAME IS REMOVED. 